There is a scarcity of follow-up studies into adult life of psychiatric disorder in young people with intellectual disability. The key aims of the present study were: (1) to determine the outcome of psychopathology present in childhood in individuals with Down's syndrome (DS); and (2) to look at childhood predictors of adult psychiatric disorder. Fifty-two young people with DS were identified from a sample of 193 subjects examined in childhood and adolescence for psychiatric and behaviour disorder. These young adults were interviewed for the presence of psychiatric disorder. No significant relationship was found between childhood mental disorder and psychiatric disorder in adult life for those individuals with DS. Early childhood factors of psychiatric disorder, challenging behaviour and family environment, except social background, did not predict adult psychopathology in young people with DS. Childhood disorder in individuals with DS has a good early prognosis with little evidence of continuity of the disorder into adult life.